schema-types

This library provides runtime and compile-type type schema definition and validation.

Features

• Zero dependencies!
• High level of developer ergonomics
• Full modern TypeScript support
• IntelliSense support

Installation

$ yarn add schema-types

Example

import * as T from 'schema-types'

// NOTE: documentation comments on the properties will appear in IntelliSense
const userType = T.object({
  /** The user's name */
  name: T.string(),

  /** The user's age */
  age: T.number(),

  /** Is the user account locked? */
  locked: T.optional(T.boolean()),
})

// Create a compile-time type alias for the schema type
type User = T.TypeOf<typeof userType>

// Use the compile-time type
export const user: User = {
  name: 'Alice',
  age: 32,
}

// Unknown data from user input, an API response, etc
const data: unknown = ...

// Return any validation issues
T.validate(userType, data) //=> [] (no issues)

T.validate(userType, {name: 'Alice', age: '32'}) //=> [{type: 'INVALID_TYPE', message: 'Invalid type, expected number, got string 32', path: '/age'}]

// Use a type-guard to refine the type
if (T.is(userType, data)) {
  // data is typed as `User`
}

// T.assert() throws an error if the data fails to validate
try {
  T.assert(userType, data)
  // data is typed as `User` (using TypeScript's `asserts` return type)
} catch (error) {
  console.log(error.issues) // logs the issues causing validation failure
}

// Generate TypeScript code for codegen
T.code(userType) //=> {"name": string; "age": number; "locked"?: (boolean | undefined)}

Type Compatibility

Types:

| TypeScript | schema-types | | ------------------- | ------------------ | | any | T.any() | | Array | T.array() | | bigint | T.bigint() | | boolean | T.boolean() | | Function | T.function() | | null | T.null() | | number | T.number() | | object | T.object() | | Record<string, T> | T.map() | | string | T.string() | | undefined | T.undefined() | | unknown | T.unknown() | | void | T.void() | | Literals | T.literal() | | Literal Union | T.literalUnion() | | Tuple | T.tuple() | | Union | T.union() | | Intersection | T.intersection() |

Modifiers:

| TypeScript | schema-types | | ---------- | -------------- | | Optional | T.optional() | | Read-only | T.readonly() |

Not implemented:

| TypeScript | schema-types | | ---------- | --------------- | | Enums | Not Implemented | | Generics | Not Implemented |

Helpers

T.TypeOf<T>

Takes a type schema and infers the TypeScript type for that schema.

T.assert(schema, value)

Checks to see if the value matches the supplied schema, and if not, throws an error.

T.is(schema, value)

Returns a boolean indicating if the value matches the supplied schema.

T.validate(schema, value)

Returns an array of validation issues, if any.

T.code(schema)

Returns a string containing the TypeScript code representation of the schema, useful for code generation.

Credits

This library was inspired by several other TypeScript runtime type libraries:

• typebox
• io-ts
• zod
• runtypes
• @punchcard/shape
• ajv

License

MIT license, see LICENSE